Lenox Place Community

Streambank Stabilization Design

Royal Consulting Services, Inc. (RCS) was requested to investigate alternative methods and design engineering services to address the degradation of an existing streambank within the Lenox Place Community, a community comprised of single family homes, townhomes, and apartments in the City of Gainesville. The streambank was approximately 13.5 feet from top of bank down to Royal Park Creek and erosion was undermining vegetation and encroaching on the nearby townhomes on the western bank and single family homes on the eastern bank.

RCS first evaluated the proposal of a soil stabilization firm and determined the proposed method of stabilization would not sufficiently address the streambank erosion issue. Lenox Master Homeowners Association then engaged RCS to evaluate existing conditions of the streambanks, complete an alternatives analysis, and design and permit the appropriate solution.

The data collection effort to determine existing conditions consisted of both survey and geotechnical investigation. The survey revealed that the overall slope of the streambank was 1 horizontal foot to 1 vertical foot (1:1 slope). The geotechnical report determined there was no immediate concern to adjacent property foundations and future concern could be alleviated by stabilizing the streambank. In general, the preliminary report noted that the cause of the slope failure was likely due to improper stormwater management and the toppling of a large tree located in the streambank.

Based on the collected information and a constructability analysis, three alternatives were proposed and evaluated, including:

• Installation of gabion baskets in a vertical wall or terraced
• Construction a sand cement bag retaining wall at the bottom of the slope
• Installing flexible concrete mats 

The client chose the first option and RCS did the final design of a gabion basket retention wall in strategic locations to prevent further erosion. The design also included active soil stabilization during establishment of grasses and routing of stormwater runoff from the nearby building. This design was completed in a very restrictive construction zone due to the proximity of the buildings to the slope and completed in a phased approach that limited sediment and erosion control issues.  This project was also streamlined through the Florida Department of Environmental Protection to obtain an Emergency Environmental Resource Permit to complete the construction. Once complete, RCS provided detail design plans, cost estimates, and bidding documents.